Here is the full list of all 27 Pax Nova achievements.
First Combat
Reach Year 2
First City
Start a game
First Science Victory
First Domination Victory
First Score Victory
First Diplomatic Victory
First Seal Victory
First War
First Human Victory
First Corvus Victory
First Drosk Victory
First Quest Victory
First Alliance
First Level 5 Unit
Reach 30 Influence
Build your first Spaceport District
Change Leadership for the first time
Assimilate Vassal for the first time
Colonize a New Planet for the first time
Build your first Outpost
Reach 40 Aether
Start a turn with 10 000 Cr
Destroy a Titan Worm
Use any Artifact
Win a game in any victory condition in the Divine difficulty mode